Analysis of Impact of Gate Bias and Oxide Thickness on Base Current Degradation From Space Radiation in Gate LPNP BJTs

The space flight data from the NASA Living with a Star (LWS) program raise questions about the basic mechanisms of radiation damage on gated lateral PNP (GLPNP) bipolar transistors (BJTs). Differences in oxide thicknesses and the presence of the gate terminal on the BJT devices under tests enable deeper analysis of the effects of space radiation damage. The data presented herein show a noticeable split in base current (IB) between the thick and thin oxide devices under 0 V gate bias measurement and a reduction of the split when -12 V gate bias is applied during measurement. This paper analyzes theIBbehavior with TCAD simulations. The postirradiation simulation structure takes into account the combination of oxide trapped charge (Not) and interfaces traps (Nit), and reduction in minority carrier lifetimes (τ) for ionization and displacement damage, respectively. Due to the difference in oxide thickness of the BJTs, the density of oxide charges (Not) and the interface traps (Nit) from ionization damage will be different, thus the data under 0 V gate bias is expected. To understand the reduction inIBsplit at -12 V gate bias, the gate sweep technique is employed to explain the effect of radiation on the base current under gate bias.